1. Field of the Invention
This invention relates to a row of slide fastener elements formed by cutting transversely a wire, which is rolled into a generally Y shape in cross section by multi-step rolling, and more particularly to a method and an apparatus for forming the slide fastener elements successively.
2. Description of the Related Art
A method for forming slide fastener elements of the above-described type is currently known. In the known method, an elongated wire having a circular cross section is rolled by a plurality of rollers into a generally Y shape in cross section, and then the rolled wire is cut by a cutting punch and a coacting cutting die into slices of element blanks, each slice having a predetermined thickness, whereupon the coupling head of each element blank is provided with a protuberance by a forming punch and a coacting forming die to finalize the individual element blank as fastener elements (hereinafter called "the wire fastener elements"). This conventional method is exemplified by EP-A0028358. The thus formed fastener elements are counted on a fastener tape successively in a predetermined pitch by calking the front and back attaching legs of each element on opposite sides of the tape by a calking punch.
According to the prior method, since the wire is rolled into a Y shape in cross section by rollers, any defective product can be eliminated to secure a very high rate of production. But since the individual fastener elements are obtained by cutting the wire into slices of a predetermined thickness by the cutting punch, the cut edges of each slice necessarily have burrs and are right-angled in cross section so that smooth beveled surfaces of the fastener elements cannot be achieved even by barrel polishing in a subsequent step.
Further, in the prior method, the opposite attaching legs of the individual element blank are bent toward each other so that each leg assumes a generally L-shape profile. When the opposite legs are calked against a fastener tape, the L-shape profile remains with the cut edges substantially rectangular in cross section after rolling, thus giving an uncomfortable touch. This drawback would be considerable in mounting the fastener elements successively on the fastener tape subsequently to the fastener element forming step. Consequently, as disclosed in EP-A0580064, it has been customary to bevel the peripheral portions of the coupling heads simultaneously with the forming of the fastener elements. In this case, it is possible to bevel the cut edges of the coupling heads, but it is impossible to bevel the L-shape profile and end edges of the leg.
In the case that the formed fastener elements are once discharged and are then mounted on the fastener tape, burrs of the formed fastener elements are removed by barrel polishing and, at the same time, their cut edges are beveled. But since the extent of beveling by this barrel polishing is limited to a minimum, a harsh touch still remains with the fastener elements mounted on the fastener tape so that an entirely smooth arcuate profile cannot be obtained.